Field of the Invention
The present invention relates to control of correction of positions of images formed on an image carrier.
Description of the Related Art
In image forming apparatuses using an electrophotographic method, a temperature increase caused by continuous image formation and the expansion/contraction of components caused by, for example, fluctuations in the environmental temperature lead to the occurrence of color misregistration, which is misalignment of relative positions of images of different colors used in image formation. In view of this, the image forming apparatuses form a test pattern that is used to detect a misregistration amount on an image carrier, and perform misregistration correction to reduce misregistration based on the result of the detection of the test pattern.
Misregistration correction is started based on a period over which an image forming apparatus operated continuously, and/or the number of recording mediums on which images have been formed. Japanese Patent Laid-Open No. 2013-25128 discloses a configuration in which, to perform misregistration correction during image formation, the image formation is temporarily suspended, an interval to the next recording medium (hereinafter referred to as a paper interval) is increased, and misregistration correction is performed by forming a test pattern in the increased interval. Japanese Patent Laid-Open No. 2006-171352 discloses a configuration in which, to perform misregistration correction during continuous image formation, a test pattern that fits within a paper interval is formed.
The configuration described in Japanese Patent Laid-Open No. 2013-25128 lowers the productivity of image formation because image formation is suspended each time misregistration correction is performed. With the configuration described in Japanese Patent Laid-Open No. 2006-171352, misregistration correction is performed while image formation is in operation. With this configuration, if a recording medium enters a nip region between a secondary transfer unit, such as a secondary transfer roller, and an intermediate transfer belt, the speed of the intermediate transfer belt could possibly deviate from a target speed. If misregistration correction is performed in a state where the speed of the intermediate transfer belt differs from the target speed, misregistration of relative positions of images cannot be corrected with high precision.